Structural variation and recovery of superconductivity by Ca substitution in Y0.4Pr0.6Ba2-xCaxCu3O7-δ

Y0.4Pr0.6Ba2−xCaxCu3O7−δ polycrystalline samples were prepared and investigated. The Ca substitution led to a structural variation toward tetragonal symmetry, possibly due to the structural modification within the Cu(1)O layer. Superconductivity and metallic conduction were recovered whenx≥0.2, giving one more evidence for the existence of the ion-size effect at the Ba site.